Spark-plug



H. F. SADGEBURY.

SPARK PLUG.

APPLICATION FILED JUNE 20. ms.

Patented Feb. 3, 1920.

UNITED STATES PATENT OFFICE.

HERMAN F. SADGEBURY, OF DAYTON, OHIO.

SPARK-PLUG.

Application filed June 20, 1918.

To all whom it may concern:

Be it known that I, HERMAN F. Simon- BURY, a citizen of the United States, residing at Dayton, in the county of Montgomery and State of Ohio, have invented certain new and useful Improvements in Spark- Plugs, of which the following is a specification.

My invention relates to explosive engines and more particularly to improvements in spark plugs therefor.

The object of the invention is to simplify the structure, as well as the means and the mode of operation of such devices whereby they will not only be cheapened in construction, but will be more eflicient in use, positive in operation and unlikely to get out of repair.

A further object of the invention is to materially increase the dielectric resistanceof the spark plug, to provide for increased radiation of heat, and to afford a compression tight structure capable of resisting high pressures.

A further object is to provide a construction in which the insulating element is removed as far as is practical from the ignition point and is so protected to some de gree against extreme temperature, and the deposit of products of combustion.

With the above primary and other inci dental objects in view as will more fully appear in the specification, the invention consists of the features of construction, the parts and combinations thereof, and the mode of operation, or their equivalents, as hereinafter described, and set forth in the claims.

Referring to the drawings, Figure 1 is a side elevation of the assembled spark plug forming the subjectv matter hereof. Fig. 2 is a longitudinal sectional view thereof. Fig. 8 is a side elevation, partly broken away of a modification of the construction shown in the preceding figures. Fig. a is an end elevation of the construction disclosed in Fig. 3.

Like parts are indicated by similar characters of reference throughout the several views.

In constructing the spark plug there is employed a bushing or sleeve 1 screw threaded exteriorly at 2 for engagement in the cylinder wall or explosion chamber, the extreme outer end of which is interiorly threaded as at 3 for the reception of the insulating element. The insulator 4: may be Specification of Letters Patent.

Patented Feb. 3, 1920.

Serial No. 240,928.

of any suitable non-electro-conducitive material. Materials such as lava, glass, porcelain, 01' other material of heat resistant characteristic may be conveniently em ployed, the particular substance forming no part of the present invention. The insulator 4: is screw threaded at its extreme inner end as at 5 for the engagement in the screw threads 3 of the bushing or sleeve 1. Inasmuch as it is commercially impossible to make such a screw threaded joint sufliciently accurate to insure a uniform compression tight engagement of successive threads, this joint is not a separable one, but the insulator is fixedly and permanently secured in its adjusted position. This is effected by means of a cement or sealing material applied to the screw threaded surfaces prior to their interengagement, which compensates for any tin-uniformity of the threads, packs the joint throughout an extended surface, and fixedly attaches the insulator and bushing. Any suitable heat resistant cement may be used. The material employed in practice is one which not only does not deteriorate under the action of heat, but is set or rendered more resistant thereby. The screw threads 8 and 5 are not essential elements of the joint but afford a convenient method of interengaging or anchoring the parts and an effective surface for the cementing opera tion. The permanent adherence of the extreme inner end of the insulator to the ex treme outer end of the bushing is the object of the joint, whatever the particular means may be for its accomplishment.

The inner end of the insulator l is provided with a bore or passage 6 extending within the insulator to a point somewhat beyond the end of the bushing or sleevel. Embedded in the insulator l and extending axially through the bore or passage 6 of the insulator is the primary electrode 7. The electrode 7 may be embedded in the insulator at the time of manufacture of the latter or maybe sealed, cemented, or otherwise fixedly mounted therein by any of the several well known methods. The outer end of the electrode is screw threaded to receive the binding nut 8. At its inner end the electrode 7 coacts with a terminal 9.

The bore or passage 6 serves several purposes. It facilitates the radiation of heat through the insulator independent of and above the bushing 1, thereby tending to maintain the electrode 7 at a lower temperature. The heated gases around the electrode mounting within the bore 6 above the limit of the bushing, are brought into closer communication with the air circulating about the exterior of the plug, and the heat is more readily dispersed through the insulator alone than through both the insulator and the bushing as in the usual construction.

Another-important function of the bore or passage (3 is the increase of the dielectric resistance due to the gap or space surrounding the electrode intermediate the electrode and the bushing. This dielectric resistance is materially increased with the increase of compression in the bore or passage 6. Many spark plugs fail through the tendency toward current leakage from the electrode to the bushing or sleeve through the insulating element. This is probably due to the dielectric resistance of the spark gap intermediate the terminals being greater when operating under a high degree of compression than that of the insulating element.

The dielectric resistance of a gap or space filled with a gas under compression is utilized in the present construction by introducing into the shortest path between the electrode 7 and the bushing 1, the gap or space afforded by the bore 6, which is of greater extent than the spark gap: between the electrode terminals 7 and 9, the current tending to follow the line of least resistance necessarily passes between the electrode terminals. In order that the current might by-pass or short circuit around the resistance gap or space afforded by the bore, it must pass a much greater distance through the insulator i. e. from a point above the end of the bore, diagonally outward to the bushing. This is equivalent to the use of an insulator of greatly increased relative sizeand efiiciency.

The insulator being connected at its extreme inner end to the extreme outer end of the bushing separates the insulator considerable distance from the sparking point, and explosion chamber, thereby reducing to the minimum the possibility of carbonized oil forming a bridge or.short circuit from the electrode to the bushing.

From the above description it will be apparent that there is thus provided a device of the character described, possessing the particular features of advantage before enumerated as desirable, but which obviously is susceptible of modification in its form, proportions, detail construction or arrangement of parts without departing from the principle involved or sacrificing any of its advantages.

While in order to comply with the statute, the invention has been described in language more or less specific as to certain structural features, it is to be understood that the in vention is not limited to the specific details shown, but that the means and construction herein described comprises but one mode of putting the invention into effect, and the invention is therefore claimed in any of its possible forms or modifications within the legitimate and valid scope of the appended claims.

Having thus described my invention, I claim 1. A spark plug, including a bushing exteriorly threaded for engagement in the wall of an ignition chamber, said bushing having a straight bore therethrough interiorly threaded at its outer end for the engagement of an insulator, an insulating body engaged therewith, the exterior and interior threaded portions of the'bushing being offset in relation one with the other whereby the inner end of the insulator is supported in spaced relation with and beyond the plane of the wall of the ignition chamber with which the exterior threads are engaged, and an electrode carried by the insulating body.

2. In a spark plug, a sleeve exteriorly threaded at its inner end for engagement with an ignition chamber and interiorly threaded at its outer end for engagement with an insulating body, an insulating body having a threaded portion extending to the inner terminal thereof for engagement with the interior threads of said sleeve, said insulating body having a central bore therein extending partially through said body and terminating beyond the outer end of the sleeve, an electrode embedded in the insulating body and extending through said bore and through the sleeve beyond the terminal of said insulating body to a point beyond the inner end of the sleeve, and a sparking point carried by the sleeve coacting with the electrode.

3. In a spark plug, a main bushing, an insulating body interengaged therewith, said insulating body having a longitudinal bore therein terminating at a medial point of said body but beyond the outer end of said bushing, an electrode embedded in said body beyond the terminus of said bore, the exposed portion of said electrode extending through said bore and thence through the bushing to a point beyond the inner end of the bushing, and a sparking finger carried by the bushing coacting with the electrode and separated therefrom a distance less than the radial extent of the space surrounding the exposed portion of the electrode within said bore.

In testimony whereof I have hereunto set my hand this 15th day of June 1918.

HERMAN F. SADGEBUR-Y.

Witnesses:

7M. A. SWANEY, F. L. WALKER. 

